The present invention relates to an automatic tool changer for automatically exchanging a tool to a machine tool such as a machining center or the like by use of a tool holder having therein a memory module to store information such as size, use time, and the like of a tool and, more particularly, to an automatic tool changer having a magnetic induction coupling apparatus for transmitting a signal between a holder and a reader/writer by a magnetic induction coupling.
As a tool holder which is used in an automatic tool changer, in U.S. Pat. Application No. 06/924,342, entitled "INFORMATION PROCESSING APPARATUS OF TOOL," and filed Oct. 24, 1986 by the inventor, and now U.S. Pat. No. 4,809,426 there is disclosed a tool holder in which a memory module is provided in the tool holder so that the holder itself has various kinds of information necessary for tool change and tool management, such as numbers, use times, and the like of the tools attached to the tool holder, and a power source is supplied from an external reader/writer to the tool holder and at the same time, data is written into or read out of the tool holder by a contactless method owing to a magnetic induction coupling.
FIGS. 1A and 1B show an example of a state in which a magnetic induction coupling apparatus for contactless data transmission is attached to a tool holder.
In FIGS. 1A and 1B, reference numeral 10 denotes a tool holder. A flange portion 14 is formed subsequent to a tapered shaft portion 12. Positioning grooves 14-1 and 14-2 are formed at two positions in the periphery of the flange portion 14. A magnetic induction coupling apparatus 16-1 is buried into a bottom portion of the positioning groove 14-1.
As shown in FIG. 2A, the magnetic induction coupling apparatus 16-1 of the tool holder 10 has a structure such that two coil grooves 20-1 and 22-1 are coaxially formed so as to open in the edge surface of a disc-shaped magnetic core 18-1 made of ferrite or the like, and induction coils 24-1 and 26-1 are wound in 15 the coil grooves 20-1 and 22-1, respectively. FIG. 2B shows a plan view of the side of a magnetic pole surface of the magnetic induction coupling apparatus 16-1 in FIG. 2A.
A magnetic induction coupling apparatus 16-2 of a reader/writer which is disposed in the outside is arranged so as to face the magnetic induction coupling apparatus 16-1 through a gap l. The magnetic induction coupling apparatus 16-2 of the reader/writer also has a structure such that induction coils 24-2 and 26-2 are wound in coil grooves 20-2 and 22-2 formed in a magnetic core 18-2 in a manner similar to the coupling apparatus 16-1.
However, the tool holder 10 with such a structure that the magnetic induction coupling apparatus 16-1 is buried in the bottom portion of the positioning groove 14-1 has the following problems. Namely, the magnetic core 16-1 and induction coils 24-1 and 26-1 cannot be made relatively large because of the dimensional limitation of the positioning groove of the tool holder 10, the electromagnetic inductive force attenuates in reverse proportion to almost the cube of a contactless transfer distance, and the like. From these reasons, the contactless transfer distance when a pair of magnetic induction coupling apparatuses 16-1 and 16-2 are disposed so as to face as shown in FIG. 2A is set to at most about 4 mm.
On the other hand, for example, in the case of a BT 50 tool holder based on the MAS standard, depths of positioning grooves 14-1 and 14-2 in the tool holder 10 are set to 14.6 mm from the outer periphery of the flange portion 14. Therefore, even if the magnetic induction coupling apparatus 16-2 of the reader/writer is disposed so as to face the magnetic induction coupling apparatus 16-1 of the holder 10 from the outside of the flange in the tool holder 10, data cannot be written into and read out of the memory module.
In the conventional automatic tool changer, as shown in FIGS. 3 and 4, tool holders 10-1, 10-2, 10-3, . . . are enclosed in racks 36-1, 36-2, 36-3, . . . of the automatic tool changer by fitting each rotation preventing stopper 34 into each positioning groove 14-2, respectively. Therefore, the magnetic induction coupling apparatus 16-2 of a reader/writer 28 is attached to the magnetic induction coupling apparatus 16-1 of the tool holder 10-2 which has moved to a predetermined writing/reading position in a manner such that the coupling apparatus 16-2 can be freely lifted up and down by an air cylinder 30 which is controlled by an air valve 32. Given to this, the following processes are executed.
(I) A desired tool holder, e.g., the tool holder 10-2 of FIGS. 3 and 4 is moved and stopped just under the air cylinder 30.
(II) After confirming that the tool holder 10-2 has been stopped, the air valve 32 is turned on to lift down the air cylinder 30.
(III) The magnetic induction coupling apparatus 16-2 is allowed to approach the magnetic induction coupling apparatus 16-1 of the tool holder 10-2 b the descent of the air cylinder 30. After confirming that both magnetic induction coupling apparatuses are located within a predetermined distance, data is written or read out. (IV) After completion of the data writing or reading operations, the air cylinder 30 is lifted up. After confirming the ascent of the air cylinder 30, the movement of the next tool holder is started.
Further, to realize the operations in the above items (I) to (IV), an elevating mechanism having the air cylinder 30 and air valve 32 must be provided for the automatic tool changer. On the other hand, prior to writing or reading data, it is necessary to execute a preparing operation to position the magnetic induction coupling apparatuses, so that the processing time becomes long. Thus, there are problems such that the structure of the mechanism becomes complicated, the cost increases, and reliability is lacking as the magnetic induction coupling apparatus is frequently lifted up and down.